Water Fight

It's one of the first chemical formulas taught in school: A water
molecule is made up of one oxygen atom and two hydrogen atoms, the
familiar H2O. But a few years ago, C. Aris C. Dreismann,
a physicist at the Technical University of Berlin, began to question
that simple ratio. At time scales of less than a femtosecond,
Dreismann and his colleagues reported observing about 30 percent
less hydrogen in water samples than expected.

Could water be, say, H1.5O at these brief scales? A crop
of news articles suggested so. But now a team at Ben-Gurion
University in Israel and Rensselaer Polytechnic University in New
York has performed an experiment similar to Dreismann's. They report
in the journal Physical Review Letters (May 13) that they
find no anomalous hydrogen levels in water and conclude that water
should be H2O at all times. Both groups are standing by
their results.

Previously in Physical Review Letters (13 October 1997)
Dreismann and his colleagues reported on their use of
neutrons, pumped up to high energies at the Rutherford Appleton
Laboratory in England, to probe water samples containing various
mixtures of hydrogen and its isotope deuterium (D), which has a
neutron in addition to a proton (a combination called a deuteron) in
its nucleus. In the same journal in 2003, they repeated the
experiment with a thin film of a hydrogen-laden polymer called
formvar, which they also bombarded with high-speed electrons at the
Australian National University. In both cases, they fired the
subatomic particles at extremely high energies at the
hydrogen-containing molecules and detected how much the particles scattered.

When they found that the particles scattered from the protons (that
is, the hydrogen nuclei) much less than expected, the physicists
surmised that the neutrons and electrons were somehow unable to
"see" the protons. At the extremely short time scales of a
neutron whizzing past—in this case 0.1 to 1
femtosecond—the theory developed that the protons might be
constantly popping in and out of a wavelike state of quantum
entanglement with their local electrons, so that on average, the
neutrons were only able to interact with the protons about half the time.

If this new type of quantum entanglement existed, it would change
many of the basic tenets of atomic physics, so the finding was
enough to make nuclear physicists—such as Raymond Moreh of
Ben-Gurion University—fall out of their chairs. Moreh felt
that Dreismann's results didn't sound right, so decided to see for
himself. He and RPI colleagues Robert C. Block, Yaron Danon and
Matthew Neuman repeated the neutron-scattering experiment with
shorter interaction times—from 0.001 to 0.01
femtosecond—as the proton-quantum-entanglement theory
predicted that the effect should be even more pronounced at shorter
time scales. In another modification, the group compared their
H2O-D2O mixture's scattering results to the
expected scattering rate for D2O. Dreismann's group had
compared the mixture to heavier atoms such as oxygen. Moreh found no
deviation from the expected scattering results: "We tried very
hard to find the anomaly, but we couldn't," he says.

Dreismann responds that Moreh's results do not disprove the original
finding, a deficit in scattering from protons; rather, since Moreh
compared protons to deuterons, the experiment shows that deuterons
undergo the same kind of entanglement. "This experiment does
not prove that protons are normal, it proves that the ratio is
normal. If you assume that the deuterons are normal, then of course
the protons are normal, but this is an assumption," says
Dreismann. "In this energy range, there is no reason, in
principle, to have a different scattering behavior for protons and deuterons."

Moreh counters that neutrons scatter from every atom differently,
and that the scattering depends more on how nuclei are oriented than
on their atomic weights. "A neutron has a very strong
scattering intensity with hydrogen, but with deuterium it has lower
scattering intensity, closer to that of oxygen," he says.
"You really have to be extremely creative to believe that
deuteron and oxygen will show a drop in the scattering intensity
exactly like hydrogen."

The disagreements go further, with the two investigators challenging
each other's calculations and questioning whether anomalies may have
arisen from equipment choices. Although Moreh considers the matter
closed, Dreismann is planning more follow-up studies, so there may
be more rough water ahead. "In the end I am very thankful that
Professor Moreh did this work, because I learned something new that
I did not know," says Dreismann. "Now I can expand my work
into faster time scales and with deuterons."—Fenella Saunders